Foundations

In a typical thermal Diels–Alder reaction, a conjugated diene and a dienophile form two σ bonds and a new π bond through a concerted cyclic pathway.

An analytical result concerns the sampled material; inference to a larger population requires a defensible sampling plan.

A detection limit specifies a decision about distinguishability from an appropriate blank or background, with a stated statistical model.

Gravimetry infers analyte amount from a measured mass or mass change and a known chemical or physical relation.

Retention factor measures time spent beyond an unretained marker relative to its transit time.

Molecular infrared absorption probes transitions between vibrational states.

Nuclear magnetic resonance distinguishes magnetically responsive nuclei in different electronic environments.

Coupled nuclear spins can split resonances into multiplets.

A mass spectrometer ionizes material, separates ions by mass-to-charge ratio and detects their abundance.

A molecular symmetry operation leaves the specified nuclear arrangement indistinguishable from its original arrangement.

In an octahedral crystal-field model, d orbitals separate into a lower t2g set and an upper eg set.

Electronic excitation between metal-centred or ligand-involving states can absorb visible light and contribute to complex colour.

Valence occupation and electronic stabilization organize main-group chemistry: alkali metals commonly form +1 ions and alkaline-earth metals +2 ions, while p-block elements support varied covalent structures and oxidation states.

In a common mononuclear two-electron oxidative addition, a substrate bond is replaced by two metal–ligand bonds and the metal's formal oxidation state increases by two.

Migratory insertion combines ligands within a metal coordination sphere, such as an alkyl and CO forming an acyl group.

A conjugated carbonyl has an electrophilic β carbon as well as a carbonyl carbon.

An ester enolate attacks another suitable ester carbonyl.

Hydride-transfer reduction of an aldehyde or ketone forms an alkoxide that can be protonated to an alcohol.

An organomagnesium reagent can transfer its carbon group to an aldehyde or ketone carbonyl, forming an alkoxide and a new carbon–carbon bond.

Oxidation of a primary alcohol can give an aldehyde or continue to a carboxylic acid, while a secondary alcohol can give a ketone.

A primary amine adds to a suitable aldehyde or ketone and dehydration of the carbinolamine produces an iminium intermediate, which can lose an N proton to give an imine.

Alcohol addition to a carbonyl forms a hemiacetal.

In a Wittig transformation, a phosphorus ylide and an aldehyde or ketone give an alkene and a phosphine oxide.

For identical sample aliquots diluted to a common final volume, blank-corrected linear response satisfies S=k(c₀V₀+cstdVstd)/Vf.

A distinct internal standard added to standards and samples permits calibration of SA/SIS=K cA/cIS, where K is the relative response.

An extraction distribution ratio D compares total solute concentrations in two immiscible phases.

In a buffered capillary, an analyte's velocity combines electrophoretic migration with electroosmotic solvent motion: v=(μep+μeo)E.

Atomic absorption measures attenuation at element-specific transitions after atomization.

Potentiometry measures the potential difference between an analyte-responsive indicator electrode and a reference electrode with negligible measurement current.

Aminoacyl-tRNA synthetases couple amino acids to cognate tRNAs using ATP-dependent activation.